Gastrointestinal system Flashcards
Components of gastorintestinal tract
oral cavity, pharynx, esophagus, stomach, large and small intestine
What are the accessory digestive organs?
Salivary glands
teeth
tounge
liver
gallbladder
pancreas
masticatory mucosa and its types of epithelium
are the gums an hard palate
composed of parakeratinized / keratinized stratified squamous epithelium
Lining mucosa and its epithelium
found on the lips, cheeks, alveolar, floor of mouth, inferior surface of tongue, and soft palate
composed of nonkeratinized/parakeratinized stratified squamous epithelium
where is specialized mucosa found?
dorsal surface of tongue
Minor salivary glands
lingual
labial
buccal
molar
palatine
Major salivary glands
parotid
submandibular
sublingual
function of serous cells
protein secretion
function of mucous cells
secrete mucin
function of intercalated duct cells
secrete HCO3-
absorb Cl-
Funtion of striated duct cells
Secrete K+ and HCO3-
absorb Na+
Parotid salivary histology
will contain excretory duct and adipose cells
submandibular salivary gland histology
contains ducts, serous cells, and mucous cells
What is the structural organization of the gastrointestinal tract (alimentary canal)?
Layers :
Mucosa
Lining epithelium
Lamina propria
Muscularis mucosae
Submucosa
Dense irregular connective tissue with vessels (blood, lymph),nerve plexus, etc.
Muscularis externa
Inner circular layer
Outer longitudinal layer
Serosa or adventitia
characteristics of esophagus histology
mucosa
submucosa
musularis externa
adventitia
what type of epithelium is found in the stomach?
simple columnar epithelium
Histological regions in the stomach
Cardia –
cardia glands produce primarily mucus
Body/Fundus –
gastric/fundic glands produce HCl and enzymes
Pylorus –
pyloric glands produce primarily mucus
Structure of Gastric/fundic glands
- Simple, branched tubular gland
- Present throughout stomach (except where cardiac and pyloric glands are)
3 regions:
Isthmus (stem cell niche)
Neck
Fundus
function of gastric/fundic glands
they produce 2L of gastric fluid a day
Fluid consists of:
- HCL
- Pepsin
- Mucus
- Intrinsic factor
- Gastrin
Types of cells in gastric/fundic glands
Mucous cells
Chief cells
Parietal cells
Enteroendocrine cells
Stem cells
The 2 types of mucous cells and their functions
Surface mucous cell:
Columnar cell
Produces/secretes mucinogen (stains with PAS)
mucus is thick, viscous, gel-like (cloudy)
high concentration of bicarbonate and potassium
Mucous neck cell:
Lines gastric pits
Produces/secretes soluble mucous (i.e. clear), less mucinogen than surface mucous cell
Secretion stimulated by vagus nerve
Characteristics of chief cells
Protein secreting (enzymes, especially pepsinogen)
Has abundant rER
Found in deep part of gland
characteristics of parietal (oxyntic) cell
Produce HCl and intrinsic factor
HCl secretion activated by gastrin, histamine, & acetylcholine
Intracellular canalicular system continuous with gland lumen Numerous microvilli
Large cells that stain with eosin (acidic dyes)
Located in neck and deep part of gland
characteristics of enteroendocrine cell
‘Open’ and ‘Closed’ cells
Secrete into the lamina propria or vasculature (not into gastric lumen)
Chemoreceptors (‘Open’ cells)
components of the small intestine
Duodenum
Jejunum
Ileum
what is the function of the small intestine and what are the structures that aid in the function?
Digestion and Absorption!!!
Aided by:
Plicae circulares (circular folds)
Villi
Microvilli
cells found in the epithelium of the small intestine
- Enterocytes
- Goblet cells
- Paneth cells
- Enteroendocrine cells
- M cells (microfold cells)
characteristics of enterocytes
intestinal absorptive columnar cells that secrete glycoprotein enzymes intp apical plasma membrane
These cell have features such as
- Microvilli
- Terminal web (contractile microfilaments in apical cytoplasm, attach to zonula adherens)
- Tight junctions
- Lateral plications (elaborate, flattened cytoplasmic processes)
characteristics of goblet cells
Produce mucus
Periodic Acid Schiff stains contents
characteristics if paneth cells
- Regulate normal bacteria flora in small intestine by secreting α-defensins (antibacterial lysozyme) that digests cell wall of some bacteria
- Located at the base of intestinal glands
- Strong eosin stain
Characteristics of Intestinal glands
a.k.a. Crypts of Lieberkuhn
Simple columnar epithelium
Tubular structures that open at the base of villi
Contain immune cells, including Paneth cells
Major component of GALT (Gut-associated lymphoid tissue)
Characteristics of M cells
M cells are the epithelial cells that overlie Peyer’s patches (lymphatic nodules)
Has microfolds on apical surface
Function :
- ‘Antigen transporting cell’
- Endocytose microorganisms (and macromolecules) from intestinal lumen, exocytose near T lymphocytes
characteristic of Peyer’s patches
composed of aggregates of lymphatic nodules within lamina propriaand submucosa
Component of GALT (gut-associated lymphatic tissue)
Prominent in ileum
Characterisitcs of Brunner’s (submucosa) glands
Glands are present in the submucosa of the duodenum
Secrete enzymes and mucous
Secretions are pH 8.1-9.3 (alkaline glycoproteins and bicarbonate)
histology of cecum and appendix
Key features of the outer surface of the large intestine/colon
Teniae coli
thickened bands of outer muscular layer
Haustra coli
sacculations between teniae coli
Omental appendices
fatty serosa projections
function of the large intestine/colon
Absorption of electrolytes and water
elimination of waste
what are the cells of the large intestine?
Intestinal Glands
Columnar absorptive cells (Enterocytes)
Goblet cells (more numerous than in small intestine)
Enteroendocrine cells
Lymphatic nodules
histology of the rectum
